1 cup (1/2 lb.) butter, softened
1 1/2 cups sugar
3 large eggs
3 large egg yolks
1 tablespoon vanilla
3 1/4 cups cake flour
2 1/2 teaspoons baking powder
1/4 teaspoon salt
1 1/4 cups milk
In a bowl, with a mixer on medium-high speed, beat butter and sugar until pale and fluffly. Add eggs, then yolks, one at a time, beating well after each addition. Beat in vanilla.
In another bowl, mix flour, baking powder, and salt. Stir about a third of the flour mixture into butter mixture. Stir in half the milk just until blended. Stir in another third of the flour mixture, then remaining milk, followed by remaining flour. pour the batter equally into two buttered and floured 9-inch round cake pans and spread until even.
Bake at 180°C or 350°F or Gas Mark 4 for 25 to 30 minutes until a skewer comes out clean. Cool on racks in pans for 10 minutes, then invert cakes onto racks and remove pans. Cool completely before frosting.
Makes two 9-inch cake layers; 12 to 16 servings